mummert and j



E. S. MUMMERT AND J. DIXON.

GRINDING MACHINE.

APPLICATION FILED NOV. 7. I919.

Patented Apr. 25, 1922.

4 SHhETS-SHEET 2.

WITNESSES ATTORNEY E. S. MUMMERT AND 1.0. DIXON.

GRINDING MACHINE.

a 93 IT E Kw 4 W pH w m4 m .a P .Qm M 7 O N D E H N W T A c U P DI A lllalllll Erwin WITNESSES ATTORNEY E. s. MUMMERT AND 1. 0. DIXON.

GRINDING MACHlNE.

APPLICATION HLED NOV. 7, 1919.

Patented Apr. 25, 1922.

4 SHEETS-SHEET 4- UNITED STATES PATENT OFFICE.

ERVIN S.

MUMMEBT AND JOSEPH O. DIXON, OF HANOVER, PENNSYLVANIA,

ASSIG-NORS TO MUMMERT-DIXON COMPANY, OF HANOVER, PENNSYLVANIA, A CORPORATION OF PENNSYLVANIA. I

GRINDING MACHINE.

Specification of Letters Patent.

Patented Apr. 25, 1922.

Application. filed November 7, 1919. Serial No. 336,341.

A. 1t and Josnri-i O. DIXON wens oi the Stains residing at hanover. in the county oi Yorl; and State oi; Pennsylvania, have invented a new and useful Grinding Machine. of which the folli'iwin jg is a specifica tion. v

This invention has reference to grinding m; :hines oi the radial tyrz and preihrably,

: h not nose "1r o i po ble type,

its object is .pro 'ide a grinding inaz 1N0 oi such t fiewhich shall be easily port able and of grt t flexi capable oi performing l coi'itiolci a single operat in accordance with the invention. the ma cnine provided with a basic struc ure carrying a superslructi turn about an up' axis, and this s? iikilll'it in turn CitillkS an ingateil arm, at onev end oi which a grinding wheel mounted. and at in other end of which there provided a dri. H means for the grimling wheel connected to the latter. and which means r'wv be a pi'ii mover in the form of an elc 1:; motor. The arm and parts carried thereby. ed uioi'intcd on 'L si )erstx':icture are or may he initially bio.- iced and pi'ovi. n is made for restoring the bu." c. sh-i For any reason. end or other oi the operation and wort: under the he moved so as: to reach p as to be moved thereon lengthwise of the arm im-e without unbalorder to vary the for an approi' ancing the structinre.

arm he or become own balanced. in order to idapt the gmnunig height of the grinding wheel from the floor or other support upon which the base rests the arm has horizontal about which it may be rocked which axis may be much nearer the motor end of the arm than the indingwheel end thereof, thus providing i'or an appropriate rise and fall of the grinding wheel. Furthermoie provision is made for twisting the grinding wheel about the longitudinal axis of the arm 0 that the point of attack of the grinding wheel may be varied angularly.

Each of the movements of the grinding wheel to different positions may be caused independently of the other movements, or in conjunction with one or more of them, whereby great flexibility is attained and the grinding wheel in its adjustments has pracuniversal movement.

The invention will be best understood tron'i a consideration of? the following detailed description taken in connection with the accit'impanying drawings forming part of this specification, with the understandlnnvever that the invention is not confined to any strict conformity with the showing in the drawings. but may be changed and modified so long as such changes and modifications mark no material departure from the salient features oi the nivei'ition as expressed in the appeni'led claims.

In the drawings,

Figure 1 is a side elevation of a grinding inaciiine embodying the invention and showing a gear drive For the grinding wheel.

Figure 2 is a loi'igitudinal vertical seclion through the machine of Figure 1, omitting certain parts and drawn on a larger scale than Figure 1.

Figure 3 is an end view of the grinding machine, with parts omitted and showing certain parts in cross section.

l ignre i; is a section'on the line 4-4 of ligure '1. showing a portion of the super structure and the basic part of the truck in elevation, the scale being the same as that of Figures 2 and 3.

Figure 5 is a side elevation of a somewhat diflerentform of the working arm carrying the grinding wheel and motor therefor but omitting the supporting truck.

Figure (3 is a plan view of the structure shown in Figure 5 and containing some of Figure 10.

Figure 12 is an elevation of the left-hand end ofthe structure shown in Figure with the handle omitted and showingthe grinding-wheel hood in section.

"Referring to the drawings, there is shown .base 1 h'aving a pedestal 2 rising therefrom, thebase and pedestal being conveniently formed as a hollow, castlng, such structure providing ample strength without undue weight. The pedestal is mounted upon pairs of supporting wheels 3 and 4, respectively, the wheels 3 being carried, by fixed axles 5, and the wheels tbeing caster wheels carried by var-Ins 6 projecting from the base 1 The wheel arrangement permits the base to be movedfabout' the floor or other supportupon which the wheels rest, with all the flexibility of movementneeded.

The topof the pedeS tal 2, which latter is a lowl pedestal, has a passage therethrough definedbyan'inturned flange 7, and extending thrcugh thisflangeis acasing 8 provided at a point intermediate of its length with an exterior circun'iferential flange 9 secured by screws 10 to the inwardly directed fiange '7, whereby the casing 8 is made fast to the top of the pedestal2 and upstands therefrom, as well'as projecting into the pedestal. Extending through the casing 8 is a hollow neck 12 extending below the bottom of the casingand havinga terminal head 13 above and overhanging the casing. At the lower end, the neck 12 has a ring l'lapplied thereto andunderriding the lower end of the casing. Between the upper and lower ends of'the'casing and the'head 13 at oine end, and the ring 14 at the other end, are antiefriction bearings 15, 16, respectively, sothat the head and neck may rotate freely in the casing,

which, in turn, ismade fast to thepedestal 2.

Fast to the head. 18'isa frame 17, of generally rectangular form, comprising two substantially rectangular side members 18, 19, which may be of web and flange construction. The head 13 is provided with oppositely-extending arms20, to which thesides 18 and19 aresecuredby screws 21 or in other suitablemannenso thatithe sidemembers' l8, 19 are carried bythe arms 20 fast to tliefhead. 13, and therefore swiveled by way of the neck 12 in the pedestal 2. At the upper end of a casing 8 are outstanding cars 22, and'the head 13 has a similar outstanding car 23 which maybe brought into alinement with an. ear 22, whereupon, by connecting the alined ears by means of a pin 24, the

superstructure 17 may be locked to the pedestal so that the superstructure will no longer swivel on the pedestal.

The two side frames 18 and 19 are connected together at the upper ends by a cross bar 25 provided with a' centrally located eyebolt 26, by means of which the entire machine may be lifted by a crane or other suitable structure, either for transportation or repairs, or for any other suitable purpose. The pin 24 is provided with an angle end 27 adapted to engage between two closely adjacent lugs 28, so that when it is not desired to have the pin 24 lock the superstructure and base of the machine together, the pin may be lifted sufficiently to disengage the parts, and the angle end 27 then dropped between the lugs28 to hold the pin elevated and out of engagement with the ear 22.

()n opposite sides of each side frame 18 and 19,are arms or brackets 29, each with inwardly directed ledges 30, those ledges on the respective frames 18 and 9 alining with each other. Carried by the ledges, whichare located on the upper portions of the brackets :30, are rack bars 31, and closely adjacent to the rack bars are tracks 32, each track having upturned ends 83 with the racks bars :31 terminating closely adjacent to such upturned ends.

.lilxtending longitudinally through the frame 17, midway of its width, is a tubular arm 34 having one end projecting far beyond the corresponding side of the frame 17, and the other end terminating within the frame. At the shorter end of the arm 34. there is secured a shelf or bracket 35 in depending relation to the arm 34 and provided with an upstanding leg 86 traversed by said short end of the arm 34 and firmly secured thereto. The shelf is of suitable size and design to receive and support an electric motor 37, which may be assumed to be fed from a suitable source of current in the customary manner. The motor 37 is provided with an armature shaft 88 connected by a coupling-v39 to drive shaft 40 extending through the hollow arm 34 and beyond that end of the latter remote from the coupling 39.

Gripping thearm 34- adjacent to the frame 17 is a clamp 41 with bolts 42, whereby the clamp may be tightened or loosened with respect to the arm 34:. Secured to, or forming part of, the clamp 11 is an extension 43 thereof carrietLaway. from the frame 17 to oneside of and parallel with the arm 34 and terminating in another clamp 44- embracing the arm 34 and capable of gripping the latter by means of a bolt 45. i

Secured to the clamp 41, by screws 46 or otherwise, is a plate 47 carrying a housing 48 extended transversely of the length of the arm 34 and terminating at the ends in roller bearing housings 49, 50. Extending through the axle housing 48 is an axle 51 carrying flanged wheels 52 at opposite ends in position to engage the track 32 and roll thereon. Secured to the wheels are gear wheels 53 at opposite ends of the axle 51 and positioned to mesh with the racks 31. The wheels 52, engaging the tracks 32,, support the arm 34 and the parts carried thereby, so that the arm 34 may be moved lengthwise through the frame 17 for a limited distance determined by the upturned stop ends of the tracks. the racks 3i, maintain the arm 34 strictly in the line of travel and prevent any side sway or movement thereof, since the gear wheels, being fast to the shaft, must turn in unison, and meshing with the racks, must maintain the proper relation to the remain-- der oi the machine, thereby compelling the arm 34, when moved lengthwise, to travel in a straight line. By loosening the clamps 41 and 44, the arm 34 may be adjusted lengthwise so that a balance is established between the end carrying the motor 37 and the other end of the arm. When the arm 34 is appropriz-itely balanced pendently from the axle 51 as a substantially horizontal axis, the arm may be very easily rocked, whereby the end oi the arm remote from the motor 37 may be raised or lowered with but little effort, the resistance to the rocking movement being reduced to a minimum by suitable roller or other anti-friction bearings located within the housings 49 and 50. Such roller bearings are not shown, since they may be of any known type suitable for the purpose.

The rocking movement of the arm 34 about the axis of the shaft 51, as well as the longitudinal movement oi? the carriage, may be controlled by a set screw or pin 54 carried by an arm 55 projecting from the housing 49 and in position to engage in a hole in the adjacent wheel 52, thus locking the arm 34 in a horizontal position when it is desired to carry the grinder about, the said arm serving the same purpose as a vehicle tongue in Shifting the machine from place to place. When the screw or pin 54 is released. the arm and its carriage may be moved in either direction through the frame 17., since then tie axle is free to turn to permit the wheels 52 to travel along the tracks 31. between the stops 33, the arm 34 being then maintained in a straight path by the connected gear wheels 53, and, it it be so desired, the arm 34 may then be rocked as needed about the axis of the axle 51.

V; the end of the arm 34, which, in Figuie and associated figures, is indicated as a The gear wheels 53, engaging" hollow rod, there is secured an elongated head 56 shown in detail in Figures 9, 10, 1i and 12. The head 56 is split longitudinally and is secured to the corresponding end of the arm 34, which enters the head tor an appropriate distance, by bolts 57. The arm 34 has a reduced continuation 58, best shown in Figure 10, entering a neck 59 extending from a block 60, The neck 59 is provided about midway of its length, or at other appropriate point, with an exterior annular flange 61, in which there is provided a circular series of radial sockets or passages 62, any one of which is adapted to be entered by a locking pin 63 extending through a boss 64 formed. on the head 56. The pin 63 is designed to secure the block 60 to the head 56 and to permit turning of the block 60 and parts carried thereby about the longititidinal axis of the arm 34, when desired.

The shaft 40 is continued through the arm 34, where carrying the head 56, and. also through the block 60, where the shaft 40 has keyed to it a bevel pinion (i5, antifriction bearings 66 being interposed between the pinion and an adjacent wall of the block (30 to serve as thrust bearings. Fast to the block (30 is a casing (37 which need not be d scribed in detail, since it serves simply the function of a housing for an arbor 63 mounted in antitriction bearings 69, 70, the arbor carrying a bevel pinion Tl. within the casing and in mesh with the pinion 65. The arbor 68 is carried through the corresponding end of the casing and turns about an axis at right angles to the axis of the shaft 40. Beyond the end of the casing through which the arbor projects, said arbor has fast to it a grinding wheel T2 held in place by the usual clamp plate 73 and nut 74. Fast to the casing 67 is a guard 7 5 on the operators side of the grinding wheel 72, which latter may be an emery wheel or any other suitable type of grinding or abrading wheel or other rotatable tool -apable of use on the machine. The casing 67 has an attaching bracket 76 and lug 77, to which is secured a grip or hand-hold 78, whereby an operator may grasp that portion of the machine carrying the grinding wheel 72 to direct it against the work to be treated.

ln order to reinforce the arm 34, which may be several feet in length. there is provided a brace member 79 in the .form of a tube with one end screwed into a lug or boss 30 on the corresponding end of the head 56, and the other end extended through the ex tremity 36 of. the shelf 35. where the brace or rod 79 has applied to it a holding member 81 indicated in Figures 1 and 2 as a pipe elbow, although not necessarily confined to sun-h fitting. The elbow 81 serves as a hold. ing means for the brace 79 and also as a mouth or entrance to the brace 79, which, being in the form of a pipe, is utilized as a and gearing.

conduit for 'tric conductors 82 connected to the motor Q The brace '79 includes a switch car HP, mounted on the arm 34; and secured thereto by. a set screw 8 1 or in other suitable manner. The carrier 88 is designed to hold :nrclect'ric switch 85, which may be of the familiar snap type or of other form and is'locatcd close to the grinding end of the arm 341- so as to be within convenient reach of an perator grasping the handle 78.

The hollow brace rod or bar 79 is arranged above the arm 8- so that the weight of the grinding end of the arm and the parts form ing such end, while tendi to bend the arm, resisted tensionally by the rod or brace 9, whereby the action of the rod79 is simi lar to that of a truss. ln order to hold the rod T9 in substantially parallel relation to the arm 34 and thereby enhance the stiffening effect, the spacebetween the rod and arm may be traversed, where needed, by bolts 86 between the endsof which and the rod and arm, clips 87 are interposed, this being shown in Figure 1'.

In the structure shown in Figure 1 and associated. figures, the power transmission from the motor to the tool, represented by the grinding wheel 72, is by way of shafts In the structures shown in Figures 5, 6, 7 and 8, a belt drive is employed between'the motor and the tool. The

didcrenccs between the two forms of power transmission constitute the principal differences between the machines as a whole, wherefore those parts of the machinewhich are not directly concerned with the type of power transmission, are not illustrated in Figures 5 to 8.

In the belt drive, an arm 3& is provided, carrying atone end a bracket 35 having an extremity 3 1 made fast to the corresponding end'of the arm 34f. At the other end of the arm 3st is a swivel head 56 held in set positionsby a pin 63 and held on the arm 3 1 by collars 88 opposite ends of the head 56. In depending relation to the head 56 is a flange or bracket 89 with an offset portion 90 carrying suitable. journal bearings for an arbor 91 for the grinding wheel 72, and also carrying the hood or guard 75 for the grinding wheel. The head 56 also carries a handle 78 which may be quite similar to the handle 78 and shown in Figures 1 and 9.

Since, in the structure of Figure land associated figures, the motor 37 has its arm a- I ture-shaft'SS" alined with the drive shaft t0, the arm 34- a-nd bracket 35 may be centralized with relation to the machine as a whole. In the belt drive form of the mar ch'ine, there is provided an electric motor 37 with a pulley 92 at the end thereof, and

this motor 87 is mounted crosswise of the machine, wherefore the bracket 35 is prop- QTlY COHS'tPUCtQCl for such purpose. The supporting leg 36 of the bracket 35 is located at one side thereof, while another similar supporting leg 36 receives a short rod or tube 93 carried by a clamp member 9% made fast to an axle housing 18, like the axle housing 4:8 of the structure of Figure 1 and associated figures. Extending through the housing 18" is an axle 51' like the axle 51, and rising from a clamp 4:1, fast to the axle housing and gripping the arm 34?, is an arm or post 95 with a cradle 96 at its upper end. Engaging bracket 97 rising from the clamp 36 is a hollow rod or tube 79 extending over the cradle 96 to a switch carrier 83 made fast to the arm 3 1i near the grinder end of the arm. The tube or hollow rod '79 constitutes a truss brace for the arm 3 1", and a conduit for conductors 82 for the motor 37, the same as in Figure .1 and ciate-d figures.

In Figure 1, the brace 79 is secured to the switch carrier 83, and, similarly, the brace 75%, Figure 5 and associated figures, is connected tothe switch carrier 835 The arbor 91 in the-structure o'f'lligure 5 and associated figures, carries a belt pulley between which and the pulley 92 there e tendsa belt 99.

Besides the handles 7 8 and 78*, the heads 56 and 56 are each provided with another handle 100 projecting from the heads on the side thereof remote from the grinding tool 72. This permits firm control of the grinding tool by a single operator.

In the structure of Figure 5 and associatediigures, the axle 51 carries track-engaging wheels 52 and gear wheels 53, the'same as in the structure of Figure 1 and associ ated figures, andthe purpose and operation thereof is the same. For this reason, it is deemed unnecessary to describe these parts separately.

In setting up the machine, or at anytime when the machine is liable to be out of balance, the clamps holding the arm 34 or 341 arc loosened su'iiiciently to permit longitudinal shifting until the motor end and the grinding end of the arm 34 or 34 are balanced, or very nearly so. Now, the machine may be moved by an operator grasping the handle 7 8 or 7 8 to an 1 point desired, where the work is to be encountered, the trucksupport of the machine facilitating such movements, and the swivel of the superstructure on the truck permitting even a relatively heavy machine to be moved with case from place to place about the shop. Vhen the machine has been suitably located, the exposed grinding edge of the grinding wheel is brought into engagement with the part to be treated by lifting or loweringthe grinding end of the arm 34L or 3 1 and by turning the head carrying the grinding tool about an axis longitudinally of the arm so much as may be needed. The grinding tool is capable of a relatively large movement without moving the truck at all since the arm 34 or 34 may be swung about the upright axis of movement of the superstructure on the truck toward any point of the compass, and moreover the effective length of the arm 34 or 34 with respect to the superstructure carrying it may be varied throughout the limits of the length of the tracks between the stops 33. The bodily movement, the circular movement, the rocking movement, the in and out movement and the twist of the grinding head about the longitudinal. axis of the supporting arm provides universal movement of the grinding head and the positioning of the latter at at any point throughout a wide area and throughout a considerable height, whereby the grinding tool may be made to act upon nearly all parts of the work without bodily movement of the supporting structure of the tool, and such bodily movement may be brought about with little effort, due to the easy running qualities of the structure, even when of considerable weight.

The arm 34 or 34*, as the case may be, is utilizableas a tongue, whereby the operator may draw the machine about the shop, and in such instance, the superstructure and pedestal are locked together by the pin 24 and the pin 54.

What 1s claimed is 1. A grinding machine comprising a hollow base, and a superstructure with grinding mechanism thereon swiveled to the base to turn about an upright axis, the swivel connection comprising a head forming the lower portion of the superstructure and provided with a depending neck entering within the base, a casing carried by and fast to the base and extendin above the base and also depending withln the same and traversed by the neck, a rin mounted on the lower end of the neck and under riding the lower end of the casing, and anti-friction bearings between the head and casing and S11 porting said head and superstructure, an also between the ring and casing to prevent lateral play of the neck in thecasin 2. A grin ing machine comprising a sup porting truck having wheels swiveled thereto, a superstructure swiveled to the truck to turn about an upright axis, means for temporarily locking the superstructure and truck together, an arm extending through the superstructure with one end terminating close to the superstructure on one side thereof and the other end projecting beyond the superstructure on the other side thereof, an electric motor carried by the short end of the arm, an axle carrying the arm adjacent to the motor end thereof, means for temporarily locking the axle from turning movement, a grinding tool carried by the long end of the arm, driving connections between the motor and grinding tool, and a manipulating handle for the grinding end of the arm, whereby when said temporary locking means are made active the long end of the arm may be utilized as a tongue for drawing and directing the machine from place to place.

A grinding machine provided with a basic portion and a superstructure, tracks on opposite sides of the superstructure, rack bars adjacent to the tracks, an arm extending through the superstructure and beyond one end thereof, an electric motor carried by one end of the arm, a tool carried by the other end of the arm, driving connections between the motor and tool, an axle carrying the arm adjacent to the motor end thereof, wheels on the ends of the axle engaging the tracks and supporting the arm from the tracks, and gear wheels fast to the axle and engaging the rack bars.

4. A grinding machine provided with a basic portion and a superstructure, tracks on opposite sides of the superstructure, rack bars adjacent to the tracks and substantially parallel with the same, an arm extending through the superstructure and beyond one end thereof, an electric motor carried by one end of the arm, a grinding tool carried by the other end of the arm, driving connections between the motor and tool, an axle carrying the arm adjacent to the motor end thereof, wheels on the ends of the axle engaging the tracks and supporting the arm from the tracks, and gear wheels fast to the axle and engaging the rack bars, the tracks having stop means at the ends to limit the travel of the wheels along the tracks.

5. A grinding machine provided with an elongateiil arm with an electric motor at one end, a grindin tool at the other end, and driving connections between the motor and tool, tracks adjacent to and on opposite sides of the motor end of the arm, rack bars adjacent to the tracks, an axle carrying said arm, wheels on the axle engaging the tracks to support the said arm from the tracks, and gear wheels on the axle and enga 'ng the rack bars to permit the longitu inal movement of the arm alon the tracks.

6. In a grinding machine, an elongated arm having an electric motor at one end, a grinding tool at the other end, supporting means for the arm on opposite sides thereof along which the arm is longitudinally movable, and means coacting with the supporting means for constraining the arm in its travel along the supporting means to a straight line, said last-named means comprising rack bars on opposite sides of the arm, and connected rotatable gear wheels engaging the rack bars, with the axis of rotation in fixed relation to the arm, whereby the engagement of the gear wheels and rack bars constrains the arm to move lengthwise without side nunsment.

7. A grinding machine comprising a sup porting structure, an arm mounted on the supporting structure to rock about a horizontal axis, and also having a longitudinal movement, driving means at one end oil? the arm, a grinding tool at the other end, oi the arm, connections between the driving means and the tool, and means located at said axis for temporarily locking the arm against both longitudinal and rocking movements.

8. A grinding machine com niising a supportin structure and an arm mounted on the supporting structure for rocking movements about a substantially horizontal axis, the mounting for the arm comprising an axle, wheels on the axle, tracks for the wheels, gear wheels on the axle, and rack bars associated with the tracks for engagement by the gear wheels.

9. grinding machine comprising a sup porting structure and an arm mounted on the supporting structure tor rocking movements about a substantially horizontal axis, the mounting for the arm comprising an axle on which the arm is pivoted, wheels on the axle, tracks for the wheels, gear wheels on the axle, rack bars associated with the tracksfor engagement by the gear wheels, and means for locking the arm against rocking movements about the axle.

10. A grinding machine comprising a supporting structure, and an arm mounted on the supporting structure for rocking movements about a substantially horizontal axis, the mounting for the arm comprising an axle, on which the arm ispivoted, wheels on the axle, tracks for the wheels, gear wheels on the axle, rack bars associated with the tracks for engagement by the gear wheels, and a short arm projecting i'romthe 1 first-mentioned arm adjacent its pivotal connection with said axle, said short arm carrying locking means to engage with one of said wheels to lock said first-mentioned arm against rocking movements about the axle.

11, A grinding machine comprising a supporting structure, an elongated arm, power 'means'at one end of and carried by the arm,

agrinding tool'at the other endoi the arm, driving connections between the power means and grinding tool, a pivotal support for the arm, and means whereby the arm may be adjusted in the direction of its length with respect to the pivotal supporting means and held in adjusted position to balance the 7 arm and parts carried thereby.

12. A grinding machine comprising an elongated arm, a supporting structure therefor, a pivotal support for the arm carried by' said structure, a motor, a bracket for supcarried thereby and then looked in its adjusted position.

13. A grinding machine comprising an elongated arm, a supporting structure thercfor, a pair of connected clamps engaging the arm at spaced points, a housing carried by one of? the clam'ps,an axle passed through the housing and constituting the pivotal axis of said arm, wheels mounted on the axle, tracks for said wheels carried by the supporting structure, a motor supported at one end of the arm at one side of said axis, a grinding tool at the other end of said arm, the said clamps gripping the arm at that side of the pivotalv axis remote from the motor, whereby the arm may be adjusted longitudinally to balance the arm and the parts carried thereby and then looked in its adjusted position.

14. A grinding machine comprising an elongated rock arm with a power unit at supporting structure and having a long end projectingf therefrom, an electric motor on one end oft the arm, a grinding tool on the other end the arm, driving connections between the electric motor andthe grinding tool, an electric switch on the arm cent to the end thereof remote from the motor, and a hollow truss or tie-rod arranged above and connected to the arm and constituting both. a brace for the arm and a eon duit for electric conductors extending from the switch to the motor. v I

16. in a grinding machine, a supporting structure, an elongated tubular arm mounted on said structure, an electric motor on one end of said arm at one side of said structure, a grinding tool. on the other end of said arm, ashaii'tcpassedthrough said arm, means connecting said shaft 'to said motor, gearing be tween said shaft and the grinding tool, a hollow rod arranged above and connected at each end to the tubular arm, that end of the rod adjacent the motor having a mouth for the insertion oi electric conductors from the motor into and. tl'lrougl'i said rod, and an electric switch carried by said rod at the end remote from said motor. a

17. In a grinding machine, a supporting structure an elongated arm, a pivot support for the arm mounted on the supporting structure and on Which pivot support the arn'i is rockable about. a horizontal axis, an electric motor carried by one end of the arm, a grinding tool carried by the other end of the arm driving connections between the motor and tool an electric switch adjacent to the end of the arm carrying the grinding tool, a post erected on the pivotal connections, and a hollow rod. connected at the ends to the end portions of the arm and extending over and. seated on the post and constituting a truss or tie-rod for the arm and a conduit for electric conductors extending from the switch to the motor.

18. Av grinding machine comprising a truck a superstructure mounted on the truck to move therewith, an elongz'tted arm mounted on the super-structure to turn about a horizontal axis a motor supported on, one end of said arm at one side of said axis, a grinding tool mounted on the other end of said (rm, driving connections between said motor and said tool and locking means located at said axis for temporarily holding said arm. against rocking moven'ients where by the rock arm is held fast to the superstructure and said arm may be used as a tongue for drawing and directing the machine from place to place.

19. A grinding machine comprising a supporting structure an elongated arm pivotally mounted on said structure a power member on one end of the arm a grinding tool at the other end of the arm, driving connections between the power member and the tool, and means whereby the arm may be adjusted lengtl'nvise of the supporting strum ture Without disturbing the pivotal connection. and made "fast to the structure in. the adjusted position to establish a balanced condition of the arm.

In testimony that We claim the foregoing as our own, We have hereto aflixed our signatures in the presence of tWo Witnesses.

EB- VIN S. MUMMERT. JOSEPH (i). DIXON.

Witnesses:

H. B. BAER, LUKE W'. ROHRBAUGH. 

